The present invention relates generally to systems for coating relatively small quantities of variously shaped materials and more particularly to systems for preparing coated tablets, pellets, or granules in quantities of from less than about 50 mg to 10 g. In a preferred embodiment, the present invention provides devices which effectively fluidize particulate materials to be spray coated by controlled vibration of a perforated bed through which drying air is passed. The methods and apparatus provided by the present invention allow for small-scale production of coated tablets, pellets or granules and are especially useful in dealing with small quantities of scarce or expensive materials, e.g., drugs during the initial stages of formulation and development.
The preparation of coated tablets, pellets and granules is a common pharmaceutical process used to mask the taste of a drug, to improve drug appearance and stability, and/or to control drug release. See, e.g., Seitz, J. A., et al.,: Ch. 12: Tablet Coating in The Theory and Practice of Industrial Pharmacy, 3rd Ed. Edited by L. Lachman, et al., Lea and Febiger, Philadelphia, 1986. The coatings are commonly applied by spraying solutions of coating material into rotating drums containing the solid dosage form of the drug or by spraying coating solutions into fluidized or spouting beds, such as Wurster columns. Fluidization of the materials to be coated is ordinarily achieved in a columnar chamber by the upward flow of drying air. While these methods are generally effective for large-scale production, they are not readily applied in small scale contexts where the drug to be coated is either not readily available in large quantities or is relatively expensive. The smallest rotating drum method currently available is believed to require use of at least 10-100 g of material to be coated and the smallest fluid bed devices currently available are believed to require a minimum of about 0.5 kg of material.
In sum, no prior devices or methods have been totally responsive to the need in the art for devices and methods allowing for the coating of small particles in quantities of ten grams or less.